An electronic part such as a solar panel, a plasma display panel (PDP), and a liquid crystal display (LCD) panel has electrode wirings formed on the substantially entire surface thereof. Such electrode wiring is formed by applying a conductive paste which contains metal particles, a glass powder, a resin binder, and a solvent to a glass substrate, a silicon substrate, or the like, and thereafter firing the applied substrate utilizing an electric furnace, a laser, or the like. At this point, the applied substrate is heated to a temperature above the softening point of the glass powder contained in the conductive paste so that the glass powder softens and flows to form tight electrode wirings and securely adheres to the substrate of glass, silicon, or the like.
For example, the manufacturing process of electronic parts such as solar panels and PDPs involves firing at high temperatures ranging from about 600° C. to about 800° C. in an oxidizing atmosphere such as the air. As a result, silver (Ag) electrode wiring, which does not oxidize even in this firing process, is often employed as electrode wirings. Being highly reliable with its excellent electrical properties, silver has the advantage of being readily formed into electrode wirings. However, there are problems associated with the use of silver: high material costs, susceptibility to migration, etc.
On the other hand, a heat treatment process in the manufacturing process of electronic parts such as large-scale integrated circuits (LSI) and LCD panels does not involve exposure to a strong oxidizing atmosphere. Therefore, pure copper (Cu) and pure aluminum (Al) are often used as an electrode wiring material for such parts. Copper and aluminum also have excellent electrical properties and the advantage of being overwhelmingly inexpensive compared to silver. Unfortunately, however, since they easily oxidize in a heat treatment in an oxidizing atmosphere, there have been limitations to their use as an electrode wiring material.
In view of the aforementioned, it has been suggested to perform some kind of anti-oxidation treatment to permit firing of a conductive paste containing copper or aluminum as a conductive component in an oxidizing atmosphere. For example, Patent Literature 1 (Japanese Patent Laid-open No. 2000-36220) discloses a conductive paste containing a copper powder and a glass frit, in which the glass frit consists primarily of boron oxide (B2O3), bismuth oxide (Bi2O3), zinc oxide (ZnO), and an alkali metal salt or alkaline-earth metal salt of a phosphoric acid.
Patent Literature 2 (Japanese Patent Laid-open No. 2008-159917) discloses a conductive paste for photoelectric conversion elements. The conductive paste contains a metal powder consisting primarily of Al and a glass powder having a glass transition point in the range of between 280° C. and 430° C. Also, in the conductive paste of Patent Literature 2, PbO (lead oxide) represents greater than or equal to 70% by weight, based on the total weight of the glass powder, and the glass powder contains at least one oxide selected from the group consisting of SiO2 (silicon oxide), B2O3, B2O3, and ZnO.
Patent Literature 3 (Japanese Patent Laid-open No. 2007-070127), with the aim of providing a Pb-free conductive bonding material for securing a spacer in a display panel of an image display device, discloses a conductive member which contains a phosphorus-based glass containing at least one element selected from the group consisting of vanadium (V), niobium (Nb), tungsten (W), molybdenum (Mo), and iron (Fe) and metal particles of silver or copper, in which the at least one element has two valences. Also, in the conductive member of Patent Literature 3, the metal particles of silver or copper represent not less than 10% and not more than 50% by volume.                Patent Literature 1: Japanese Patent Laid-open No. 2000-36220        Patent Literature 2: Japanese Patent Laid-open No. 2008-159917        Patent Literature 3: Japanese Patent Laid-open No. 2007-070127        